This invention relates to a device for extracting wire rod or the like at the outlet end of a rolling mill, and more particularly to a device for extracting the end portion of wire rod or the like from the laying guide of an Edenborn type of coiler intended for coiling the wire rod in loose turns at a rolling mill outlet.
The device is intended for use with a rolling mill operating intermittently starting from billets, or with a continuously operated rolling mill located downstream of a continuous casting machine.
As is known, an Edenborn type of coiler comprises a rotary laying cone, provided with a tubular laying guide the inlet portion of which is disposed aligned with the guide end portion which normally connects the rolling mill to the coiler, and the outlet portion of which is substantially tangent to the base circle of the laying cone and slightly inclined downwardly. The wire rod from the rolling mill, guided by the laying guide, is deposited in the form of a cylindrical coil as a result of the laying guide rotary motion overlapping the forward movement of the wire rod. The turns forming the cylindrical coil may be deposited directly on a continuous conveyor, which carries them to collecting baskets or other collecting means.
A collecting system of this type is described in U.K. Patent Specification No. 1,417,009 of the same applicant, in which part of the conveyor and coiler is immersed in water to prevent the wire rod oxidizing.
This wire rod collecting system is particularly suitable for rolling mills of high production speed, as is the case of modern wire rod rolling mills.
However, this system has a disadvantage which up to the present time it has not been possible to satisfactorily eliminate, and which occurs in particular when operating under low speed conditions with small diameter wire rod. In this respect, at the end of each working cycle (and thus very often when the rolling mill operates discontinuously starting from billets) the last few meters of rolled wire rod, which constitute the wire rod end portion, leave the last rolling assembly and the conveying means upstream of the coiler, and proceed into the laying guide only by the effect of their force of inertia, which is opposed by the friction force arising as the wire rod rubs against the inner surface of the laying guide.
At low speeds and small rod diameters, and thus with only a small moving mass, the wire rod inertia is not sufficient to overcome the friction force, because of which the wire rod end portion stops in the laying guide which, continuing to rotate, takes up the already deposited rod, twisting it and unwinding the turns lastly deposited, with considerable economical damage both in terms of the loss of part of the production and the time necessary to restore the efficiency of the plant.
This phenomenon may also occur in the case of higher speeds and larger diameters when there are no conveying means upstream of the coiler, the wire rod then being thrust by the rolls of the last rolling assembly.
Various methods have been studied for preventing this disadvantage, but they are either considerably complicated in construction and therefore of high cost, or do not act automatically, even through some are effective in extracting the wire rod.
One of these methods consists of guiding the wire rod immediately downstream of the outlet section of the laying guide between the inner wall of a fixed cylinder of internal diameter equal to the external diameter of the turns being formed, and a roller disposed inside the turns and rotatably supported by a swinging arm the pivot of which is rigid with the laying cone, and gripping the wire rod between the cylinder wall and roller at the moment of extraction, by thrusting the roller against the cylinder by a mechanical or electromagnetic control. By gripping the wire rod, it is prevented from assuming the same speed as the laying cone and the wire rod is therefore disengaged from the laying cone.
The main disadvantage of this device is that the roller does not operate automatically, but at a command by an operator. This is an important point, especially when the plant stoppage is not programmed. This manual operation requires a certain ability for intervening at the correct moment and definitely preventing any starting of the described twisting.
Other devices are known which dispense with the intervention of the operator, and use extraction devices arranged to remain in operation during the entire processing, but these devices introduce mechanical stresses and friction which are undesirable, and also represent complex solutions of complicated construction and therefore decidedly costly.